.357 Magnum (semi auto)
M1 (left click) to shoot, M2 (right click) to use iron sights.

Crossbow (auto)
M1 to shoot, M2 to use scope.

Crowbar (auto)
M1 to swing

Frag Gnade
M1 to throw, M2 to drop gently.

Glock 17 (auto)
M1 to shoot slow, M2 to shoot fast.

Gluon Gun (auto)
M1 to shoot

Hivehand/Hornet Gun (auto)
M1 to shoot, M2 to shoot with direction??

MP5 (auto)
M1 to shoot, M2 to shoot gnade.

RPG
M1 to shoot, M2 to turn laser on/off. (when laser is on you can steer the rocket)

Spas-12 (auto)
M1 to shoot, M2 to shoot two shots.

Tau Cannon/Gauss Gun (auto)
M1 to shoot, M2 to charge your shot.